The invention relates to an improved ladder clamp for holding a ladder to roof bars of a vehicle and a method thereof.
Ladder clamps are known. A typical ladder clamp 10 is shown in FIGS. 1-3. As shown, a ladder clamp 10 is used to hold either end of a ladder 11 to a vehicle's roof bars 12. Here, each ladder clamp 10 includes a generally hooked shaped part 20 having a hook 22 for hooking underneath the roof bar 12 and an elongated portion 24 that extends up and away from the roof bar. The elongated portion 24 has a thread down its length. The thread is typically machined or rolled. An oversized wing nut 30 having upstanding handles 32 is screwable up and down the thread of the elongated portion 24. In use the ladder is placed on the roof bars 12. The hook part 20 is arranged under the roof bar and a clamp bar 40 fitted over the top of the ladder by inserting an end of the elongated portion 24 through an aperture in the clamp part 40 so that the clamp bar 40 can slide down the elongated portion. The wing nut 30 is subsequently twisted about the elongated portion to tighten down on the clamp bar 40 in order to securely hold the ladder in place. Two protrusions 41, 42 restrict side-to-side movement of the ladder 11. A lock 50 can be used to stop unauthorized removal of the ladder.
The threaded coupling between the elongate portion 24 and the oversized wing nut 30 has been found to be slow to use and not particularly easy to use. For instance, to move the wing nut sufficiently to remove the ladder clamp, the wing nut has to be rotated many times. This is time consuming and not particularly convenient. Also, the thread is prone to damage. For instance, the threads can corrode (e.g. rust) or the threads can become mechanically deformed from mishandling the parts or from other parts contacting them. In each event, the threaded connection fails causing the ladder clamp to have to be replaced.